Plunger switch



Feb. 14, 1961 c. A. wooDcocK PLUNGER SWITCH A Filed Aug. 18, 1958 United States Patent PLUNGER SWITCH Charles A. Woodcock, Springfield, Ill., assignor to Stewart-Warner Corporation, Chicago, Ill., a corporation of Virginia lFiled Aug. 18, 1958, Ser. No. 755,569

6 Claims. (Cl. 200-159) This invention relates to electrical switches, and more particularly to a plunger-type switch which is especially adapted for use where the switch is to be actuated by the opening and closing of a door or other closure means.

In the past, switch constructions have been actuated by the opening and closing of closure means such as a door, for operating a lighting circuit or other electrical circuits. As such, the switch must be mounted in proxirnity to the door so vthat the circuit is energized or deenergized immediately upon opening or closing of the door. Plunger-type switches are commonly used where the plunger is adapted to be in direct contact with the moving surface of the door structure so that any movement of the door will result in an instantaneous movement of the switch plunger. However, such known constructions have been somewhat complicated and have required a relatively large number of parts to constitute a suiciently sturdy, workable and reliable switch.

It is, therefore, an object of this invention to provide an improved plunger-type switch in which the number of parts required are greatly reduced.

It is a further object of this invention to provide an improved plunger-type switch which is easier to assemble and in which the cost per unit switch is greatly reduced.

Further objects and advantages of this invention will become apparent as the following description proceeds.

In accordance with one form of this invention, there is provided a supporting bracket including a pair of spaced, upstanding lugs formed therein, the lugs having aligned apertures for holding a plunger which is slidably positioned therein for reciprocatory movement. One of the lugs forms the stationary contact member of the switch while the moving contact member comprises a cylindrical ferrule which is positioned on one end of the moving plunger on the outer side of the lug forming the stationary contact. The ferrule is spaced from the conductive plunger by means of an insulator. The ferrule is normally biased against the stationary contact lug member by a compression spring which surrounds the portion of the plunger between the two lugs.

For a better understanding of this invention, reference may be had to the accompanying drawing in which:

Figure l is a perspective View of the plunger-type switch embodying one form of. this invention;

Figure 2 is a top view partially in section of the switch shown in Figure l;

Figure 3 is an exploded view of vthe plunger and its associated parts which are utilized in the switch shown in Figures 1 and 2.

Referring now to the drawing, there'is shown a plungertype switch including a support bracket or base which is indicated generally at 10. The support bracket has a generally i'lattened base portion 12 which includes a slot or aperture 14 to allow the support bracket to be attached to a vdoor frame or other like member, depending upon the particular application in which the plunger-type switch is used. There is also formed on one end of the support bracket 10 a depending flange portion 16 which is normally associated with such switches as a means for locating the switch support along the edge of the door frame. At the side of the support bracket opposite the aperture and the locating ange, there is a iirst upstanding supporting lug 18 and a second upstanding supporting lug 20 at either end of the support bracket, the lugs being integral with the base portion 12 of the support bracket 10. The upstanding lugs 18 and 20 and the depending ange 16 may be formed on the support bracket by any conventional method such as by die-forming. In order to support a plunger 30 for reciprocatory or axial movement with respect to the stationary support bracket 10, there is provided an aperture 22 formed within lug 18 and an aperture 24 formed within lug 20. The diameter of the apertures is determined by the particular diameter of the portion of the plunger 39 passing respectively through each aperture. lt will be noted from Figure 2 that the diameter of the aperture-24 is somewhat larger than that of aperture 22 and, in addition, that the aperture 22 is so formed within the first supporting lug 18 that a portion 2S of the lug immediately surrounding aperture 22 is directed generally outwardly for purposes which will be described in detail hereinafter.

The plunger 3G is essentially of rod-like or cylindrical shape, and is preferably constructed of steel or other relatively hard material. As indicated in the exploded view, Figure 3, the plunger 30 includes three portions of varying diameter, the upper portion 32 having a somewhat larger diameter than the intermediate portion 34 and terminating in a reduced diameter portion 36. Thus, there is provided a shoulder 38 between the large diameter portion 32 and the intermediate diameter portion 34 and a shoulder 39 between the intermediate diameter portion 34 and the small diameter portion 36. As shown in Figure 2, a compression spring 4t) of spring steel or the like, is positioned on the plunger 30 and surrounds the intermediate diameter portion 34. The compression spring is placed on the plunger during the assembly process after the plunger is inserted through the larger aperture 24 formed in lug 2t) and prior to the plunger being inserted within the smaller aperture 22. Thus, one end of the compression spring 40 abuts against shoulder 38 while the other end of the compression spring abuts against the inner surface of the supporting lug 18 so as to generally bias the plunger in a direction opposite to that in which it is inserted.

ln the embodiment shown, the first supporting lug 18 forms the stationary contact for the switch. The moving contact of the switch is provided by securing a conductive metal ferrule 42 to the small diameter portion 36 of the plunger 30. To prevent a short circuit from occurring between the metallic ferrule member 42 through the metallic plunger 3d to the stationary contact formed on lug 18, there is provided an intermediate non-couductive member or cylinder 44 between the ferrule 42 and the small diameter portion 36 of the plunger. The

ferrule includes a reduced diameter portion 46 at the outer end thereof which prevents any movement of the intermediate non-conductive member 44 in that direction. in the present embodiment, a pair of indentations 47 are formed in the ferrule at its inner end adjacent the inner end of the intermediate non-conductive member 44 so as to prevent relative movement between the ferrule and the non-conductive intermediate member in that direction. To allow the ferrule to be readily placed upon the non-conductive intermediate cylindrical member 44, as well as to provide a resilient female connector at the outer tip portion of the ferrule, there is provided a slot 48 which is formed throughout the length of the ferrule and allows easy insertion of a male connector member (not shown) to connect the switch into an appropriate electrical circuit. In order to provide a greater contact surface area for the moving and stationary contacts, the inner portion of the ferrule is ared outwardly at 5@ so that it conforms to the outwardly ared portion 28 or contact surface of the first supporting lu'g 13.

ln the embodiment shown, the intermediate non-conductive member 44 which is positioned between the small diameter portion of the plunger and the ferrule 42 or moving contact member, is attached to the plunger by a suitable cement. Various other methods may be employed for securing the intermediate member to both the ferrule and the moving plunger. For instance, indentations may be made in the larger diameter portion of the ferrule so as to form like indentations in the plastic non-conductive intermediate member and thus prevent any movement between these members. These indentations in addition to the natural compressive forces which are set up by the slotted ferrule also help retain the ferrule upon the intermediate member 44.

The particular lengths of the plunger portions are determined so that the plunger when in assembled position, has the large diameter portion 32 always positioned within the aperture 24 formed within the second lug 20, and the intermediate portion of the plunger always located within the smaller aperture 22 formed within the first lug 1S, regardless of whether the switch is in its open or closed position.

While there is shown a plunger-type switch in which all of the elements-are made of conductive material with the exception of member 44, the switch may be so constructed that the plunger itself is non-conductive, while the support bracket and the ferrule are of normal conductive materials. rIn this regard, there would be no need to utilize an intermediate non-conductive member such as cylinder 44. The operation of the device forming the present invention may be adequately seen by reference to Figures l and 2, Figure 1 showing the switch in closed position, whereas Figure 2 shows the switch in open position. In Figure 1, the switch is normally biased in the closed position, that is, the compressive spring 49 exerts a force on the plunger Sil tending to move the plunger from left to right whereby the ferrule 42 is biased against the stationary contact ZS formed in supporting lug 18. The switch is operated by movement of the plunger against the bias of the compression spring 40, for instance, by closing of an automobile door (not shown) wherein one portion of the moving door is adapted to strike the end 52 of the large diameter portion of the plunger so that the plunger and its rigidly associated ferrule 42 are moved away from the stationary contact 2S 0r supporting lug 18. Under such circumstances, whenever the automobile door is closed the switch will be in an inoperative or open position, while opening of the door will allow the compression spring to move the plunger 30 from left to right and close the switch contacts, completing an electrical circuit to an appropriate light associated with the door.

While the'particular embodiment shown in the accompanying drawings may be utilized effectively in applications employing vehicle doors, the switch has many other like uses and may be used in conjunction with refrigerators, cabinets and the like. The switch may also be used in any application employing one stationary element and one moving element wherein it is desired to connect or disconnect a circuit as a result of relative movement between the two elements.

While there is shown and described a speciiic embodiment of this invention, it is not desired that this invention be limited to the particular construction shown and described and it is intended by the appended claims to cover all modications within the spirit and scope of this invention.

What is claimed is: Y

l. A plunger-type switch comprising; a supporting bracket including a first and second upstanding lug, said first lug forming the stationary contact of said switch, aligned apertures formed in said lugs, a plunger mounted on said bracket and extending through said apertures for axial movement therein, a compression spring surrounding said plunger and positioned between said lugs, a generally cylindrical ferrule mounted on said plunger, said ferrule being positioned on said plunger on the side of saidtirst lug opposite that of said compression spring, said compression spring acting to normally bias said ferrule against said first lug, whereby said ferrule forms said moving contact with said switch.

2. A plunger-type switch comprising; a plunger having a first switch contact carried by said plunger, a supporting bracket including at least one upstanding lug to support said plunger for axial movement thereon, said lug constituting a second switch contact, and resilient means to normally bias said plunger to close said contacts.

3. A plunger-type switch comprising; a plunger having a first switch contact carried by said plunger, means to support said plunger for reciprocatory axial movement, said support means including a pair of spaced upstanding lugs members, said plunger -being mounted on said lugs for axial movement therein, one of said lug members constituting a second switch contact and both of said lug members constituting a plunger guide bearing, and resilient means to normally bias said plunger to close said contacts.

4. A plunger-type switch comprising; a plunger having a first switch contact carried thereon, a supporting bracket including a. pair Vof upstanding lugs, apertures formed within said lugs whereby said plunger is mounted within said apertures for axial movement therein, a compression spring surrounding said plunger and positioned between said lugs, one of said lugs constituting a second switch contact, said compression spring normally biasing said plunger to close said contacts.

5. A plunger-type switch comprising; a supporting bracket including spaced first and Ysecond upstanding lugs, said first lug forming the stationary contact of said switch, aligned apertures formed in said lugs, a plunger mounted on said bracket and extending through said apertures for axial movement therein, a generally cylindrical ferrule mounted on said plunger and spaced and insulated therefrom by an intermediate non-conductive member, a compression spring surrounding said plunger and positioned between said lugs and acting to normally bias said ferrule against said first lug whereby said ferv rule forms said moving contact of said switch.

6. A plunger-type switch comprising; a supporting bracket including spaced irst and second upstanding lugs,

each of said lugs having an aperture formed therein,

the aperture formed in said first lug being smaller than that formed in said second, said rst lug forming the stationary contact of said switch, a plunger mounted on said bracket and extending through said apertures for reciprocatory movement therein, said plunger having three stepped portions of differing diameter including an end portion of greatest diameter, an intermediate portion of somewhat smaller diameter, and another end portion of smallest diameter, whereby rst and second shoulders are formed on said plunger, said plunger being mounted within said apertures so that said largest diameter portion of said plunger is positioned within the aperture formed within said second lug and the intermediate diameter porticn of said plunger is positioned within the aperture formed within said iirst lug, a compression spring surrounding said plunger and positioned between said lugs with one end of said compression spring abutting said rst shoulder, and the other end of said compression spring abutting the inner surface of said first upstanding lug, a generally cylindrical ferrule mounted on said plunger at said smallest diameter portion and insulated therefrom, said ferrule being positioned on said plunger on the side of said first lug opposite that of said compression spring, said compression spring acting to normally bias said ferrule against said rst lug whereby said ferrule forms the moving Contact of said switch.

vReferences Cited in the le of this patent UNITED STATES PATENTS Liley June 9, 1953 2,727,954 Higbie et al. Dec. 20, 1955 2,835,760 Ringwald May 20, 1958 

